KABUL -- Six U.S. service members died in separate attacks in Afghanistan on Saturday, another round of killings in what is shaping up to be the most violent summer of the nearly nine-year war.

The troops died from diverse causes, including homemade bombs, gunfire and an accidental explosion. Four were killed in eastern Afghanistan and the others in southern Afghanistan, the two regions of the country where the Taliban insurgency is strongest.

Both deaths in the south were caused by roadside bombs; those in the east involved bombings, small-arms fire, an unspecified insurgent attack and the accidental blast, according to NATO statements. On the day deaths occur, few details are released about the incidents until families are notified.

NATO convoys in the north and east were also the targets of bombings Saturday, but there were no reported deaths.

This month, 23 U.S. soldiers have been killed in Afghanistan. Last month was the deadliest of the war, with 102 NATO soldiers dying, including 60 Americans, according to the Web site http://icasualties.org, which tracks fatalities in Iraq and Afghanistan.

Summer is the season when insurgent aggression intensifies, as the thawing snow allows greater freedom of movement in the mountains. Military officials also attribute the rising violence of recent weeks to the 30,000 new U.S. troops who have arrived or are on their way to Afghanistan, pushing into insurgent havens where the coalition has had little or no presence before.

Afghan civilians have also been among the victims of the violence. On Saturday, 11 Pakistanis were gunned down in the Paktia province, on the Afghan-Pakistani border, after they crossed into Afghanistan to shop, the Associated Press reported. The slain civilians were Shiite Muslims.